The development of color-related products frequently involves a coordinated effort of assorted color product development specialists, such as manufacturers, designers, printers, ink manufacturers, dye manufacturers, paint manufacturers and material suppliers. Demand for products and services provided by these businesses originates from many industries, including cosmetics, plastics, textiles and the food industry. A great deal of communication between the contributors to a color product can be expensive and time burdensome. Frequently, the communication between the contributors to a color product can be expensive and time burdensome. Frequently, the communication comprises physically handling the delivery of samples for approval during the several developmental stages in the production chain.
During creation of color products, many samples are packaged and delivered to many different parties for approval. For example, a designer provides physical design samples to a manufacturing company for approval, a plate separator converts digital and/or analog images into a form of printing plates or cylinders and submits proofs to a designer or manufacturer, a formulator submits proofs to a printer, and printer submits samples to a designer and/or manufacture for approval. Physical models of the design and prospective future appearances are included in the package.
In the event that any one sample is unacceptable, for example, because it varies from the original specifications, then a party relying on the sample usually insists upon revisions. Whenever revisions to a sample are made, new samples typically are provided for additional review.
For example, a printer may require products and services from material suppliers, including ink manufacturers, dyers, separators and the like. Potentially expensive packages containing samples, prototypes and documents relating to each party's respective involvement are transferred between the parties. Physical packages typically require approval in a particular sequence during development in the production chain. Reliance upon a particular schedule increases the impact of delays caused by a lengthy sample creation and acceptance process. Moreover, samples that are rejected after several stages of development have already been approved can result in changes that impact those previously approved stages.
Electronic color production hardware and software systems currently exist which separately and independently perform many of the tasks required in the above-described production chain. For example, a known system reads visible spectrum of a color sample and generates data directed to measured amounts of light absorbed or reflected at particular points in the spectrum. Any given color has a spectral curve associated with it that functions as a signature of the color. Once a spectral curve is determined, the visible spectrum and coefficients are then processed to predict a color formula for reproducing the color. This measuring technique is more accurate than, for example, the colorimetric approach to color representation because the colors will appear the same in any lighting environment.
The calorimetric representation is a numeric method (CIELAB) of representing a color, wherein “L” represents the lightness to darkness of a color, “A” represents the redness to greenness of a color and “B” represents the yellowness to blueness of a color. The values of similarity between colors is determined by calculating the sum of the squares of the differences between the L, A and B values. This method is not as comprehensive as determining spectral curves for a color because the values are applicable for only one lighting condition. Differing lighting conditions can product different shades of color, and then a new set of CIELAB values.
Other common color representations exist, for example RGB represents the degree of red, green and blue in a color. CMYK represents the degree of cyan, magenta, yellow and black in a given color. Accurate translation between color representations, for example a translation from RGB to CMYK for computer monitors and computer printers is provided. Accurate color reproduction is achieved, in part, by retrieving data for a plurality of input and output devices, e.g., printers, monitors, and color measuring devices, and modifying the color translation formulas to account for the specific devices receiving the data.
Another known system provides a method and apparatus for accurately matching colors. For example, spectral data are received from a color measuring device and the corresponding color is matched in an electronic color library. The desired color is compared to colors stored in the electronic color library and the color or colors in the library that are within a specified color range are reported. By searching in an electronic library, the traditional standard color swatch book used for locating a desired color is replaced. This electronic color library is vulnerable, however, to problems associated with producing samples from multiple devices.
Another method involves receiving a communication of the designer's computer image and converting the RGB setting to CIELAB values. Computer software design packages such as ADOBE® PHOTOSHOP® and ADOBE® PAGEMAKER® provide such conversion functionality.
EP 00974225 and U.S. Pat. No. 5,933,578, describe a method for predicting the color of two or more overprinted inks in halftone, and a method for modeling the tone scale value of spot inks by reading the spectral reflectance of halftone patches printed over a white, gray and black substrate.
U.S. Pat. No. 6,310,698 and WO 1086943, describe a method to model the tone curve of one print device in order to reproduce the tone curve of another print device. The system automates the process of creating plate curves for a printing system from a design proof with a known tone value curve and compensates for differences in optical and mechanical dot gain by building a look-up table for multiple screening frequencies.
The assemblage of mutually distinct and often disparate methods, samples, and goods as encountered in the current prior art can potentially result in errors and delays in the process. Each communication delay frustrates the color reproduction process and can result in the associated parties trying to identify a party to be held liable.
Current color formulation technology does not meet some market needs as the emphasis is on matching only the solid ink color. As color markets now often take advantage of the both the solid color value and less saturated tone values (halftone, error diffusion and other pattern-generation methodology) in order to add depth and image detail in the coloring process, a method of formulating a match to both a solid color and one or more tone values of the same color can bring improved repeatability to the coloring process. This approach can also aid in obtaining formulae that result in color matches between disparate materials coloring/imaging processes and end-use applications.
Due to their linear nature (see FIG. 10) at the various halftone steps (i.e. from 100% tone strength all the way down to 0%), mono-pigmented CMYK process colors allow for the prediction of ink color formulae that accurately reproduce color standards.
The current state of the art also allows for reliable prediction of formulae for producing multi-pigmented spot colors (henceforth “brand colors”) that accurately match a standard at 100% tone strength (AKA solid color). Note: “Brand colors” refers to customer-specific multi-pigmented colors often associated with a specific product or brand name. Brand colors are sometimes referred to as “special colors”. However, when this same brand color is printed at various halftone values, it often no longer matches the brand color standard due to the non-linear nature of multi-pigmented brand colors when printed at various halftone values (see FIGS. 11 & 12). Thus, a need exists for a system that can accurately predict a color formula that will match a brand color standard at both 100% tone strength as well as at any of the halftone steps up to the 100% tone value (e.g. 5%, 10%, 15% halftones, etc.).